On Thu, Jun 06, 2019 at 07:53:29PM -0400, Michael Meissner wrote:
> On Thu, Jun 06, 2019 at 06:14:29PM -0500, Segher Boessenkool wrote:
> > On Thu, Jun 06, 2019 at 06:42:16PM -0400, Michael Meissner wrote:
> > > 2019-06-06 Michael Meissner <meiss...@linux.ibm.com>
> > > -mpcrel automatically sets -mcpu=future and -mprefixed-addr, and
> >
> > Automatically setting -mcpu= is a bad thing. Instead, we should just
> > error out if someone tries to use -mpcrel with a CPU (or ABI, etc.) that
> > doesn't support it. Or, is there any special reason you want it?
>
> Well, I was trying to be consistant with the other things (-mpower9-vector
> automaically sets all of the other power9 options).
Yes, and that is no end of pain. It's better than just enabling *some*
of the p9 insns, sure.
> As I mentioned elsewhere, there is a real problem with options specified on
> the
> command line and pragma/attribute target (basically if you set -mpcrel on the
> command line, and then do '#pragma GCC target ("cpu=power9")', it will
> currently complain that -mfuture or -mcpu=future is not set.
That, for example.
> > In the future, we will not have an -mprefixed-addr option (it will be
> > always on for CPUs that support it), and I don't see any real reason
> > to allow disabling pcrel either, but we'll see.
>
> Well I suspect for at least several months we will need the ability to turn
> off
> pc-relative support but allow the other future stuff.
Oh certainly. But we should keep the eventual goal in mind, and structure
things for *that*, where possible.
Segher
